Tremendous disparities are known to exist in cardiovascular disease and its related outcomes. Much of this can be traced to poorly controlled hypertension and its attendant, pressure-related consequences, especially target-organ cardiac damage. The latter, which occurs prematurely and disproportionately in African- Americans, reduces both quality and quantity of life. The risk of target-organ cardiac damage is particularly high among inner-city African-Americans with hypertension, particularly those who utilize the emergency department for chronic blood pressure management. Like cardiovascular disease, vitamin D deficiency disproportionately affects African-Americans. Vitamin D is thought to be an important modifier of cardiovascular disparities through its direct (and, via parathyroid hormone, indirect) myocardial (hypertrophy, fibrosis) and vascular (increased resistance, loss of compliance) effects. Vitamin D repletion in those who are deficient has been postulated as mechanism to reduce the cardiovascular disease burden experienced by African- Americans, especially if initiated early before irreversible damage has occurred, but this has yet to be tested in a prospective clinical trial. Accordingly, this proposal was designed to investigate the relationship between vitamin D and subclinical target-organ cardiac damage (as identified on cardiac magnetic resonance imaging) in a cohort of African-American, vitamin D deficient hypertensive patients without prior history of heart disease. Specifically, we seek to ascertain the effect of adjunct vitamin D therapy on left ventricular hypertrophy (primary aim), myocardial fibrosis and central vascular function (secondary aims) at one-year using a placebo controlled, randomized design. Antihypertensive treatment in both study arms will be standardized and our focus will be recruitment of patients who present to our safety-net institution with poorly controlled blood pressure - a high-risk, high-reward subset who would stand to benefit tremendously from identification of an inexpensive intervention, which could effectively reduce the adverse impact of hypertension. PUBLIC HEALTH RELEVANCE: African-Americans die younger and more often from hypertension and hypertensive heart disease than other races. Regression of left ventricular hypertrophy, a cardinal manifestation of elevated blood pressure, which disproportionately affects African-Americans, can reduce adverse events and, accordingly, has become a focal point of secondary prevention. Vitamin D deficiency may be an important contributor to racial differences in hypertensive heart disease but whether adjunct vitamin D therapy provides benefit is unknown.